I have dents up and down my shins from 12 years ago, when I did Muay Thai. Before that, I had some weird separation of the tendon and shinbone (Osgood Schlotters, I think) that made my shins super-sensitive. After conditioning my shins, they are not sensitive at all. The dents don't feel any worse. I dont see how you can avoid the dents if you seriously do kickboxing.

no worries, in fact it helps, i've been fighting for 10+ years, my shins are a little wacky, it works GREAT

i think it's kinda like a sword or a pinpoint attack, your putting a buncha pressure in a specific area.

i've just gotten used to kicking with a certain region of my shin, good times.

from a medical stand point (i'm only a second year student so don't take my word) - calicified bone is the best! less chance of break, it's harder so it as less give, and it has less nerves so you feel less pain. (i've done the bottle rolling trick so my pain sensativity is way the hell low anyway but it's a good thing!)